As known, an optical disc drive has an optical pickup head for projecting a laser beam onto a rotating optical disc. According to the reflected laser beam, the optical disc drive generates various electronic signals (e.g. a radio frequency signal RF, a tracking error signal TE and a focusing error signal FE). According to these electronic signals, the data stored in the optical disc are acquired and the optical pickup head can be correspondingly controlled. In addition, during the process of reading data from the optical disc or writing data into the optical disc by the optical pickup head, the data reading/writing quality is highly dependent on a tilt of the optical pickup head.
Generally, after the optical pickup head is fabricated, the optimal tilt is slightly deviated or shifted. Consequently, after the optical pickup head is assembled in the manufacturer of the optical disc drive, the tilt of the optical pickup head should be adjusted to result in an optimal angle between the optical disc and the optical pickup head. Due to the optimal angle, the laser beam emitted by the optical pickup head can be vertically projected onto the optical disc, and thus the data reading/writing quality is enhanced.
FIG. 1 is a schematic perspective view illustrating an optical pickup head of an optical disc drive according to the prior art. As shown in FIG. 1, the optical pickup head 100 has a lens 110 for projecting a laser beam and receiving the reflected laser beam. The optical pickup head 100 further comprises two rail holes 102, 104 and a rail notch 106. Through the rail holes 102, 104 and the rail notch 106, the optical pickup head 100 is supported by two guide rails 210, 220 (see FIG. 2) and movable on these two guide rails 210, 220.
Please refer to FIG. 1 again. Generally, the tilt of the optical pickup head 100 is adjusted by controlling the tilt angle of the XY-plane, i.e. by adjusting a radial tilt angle (RAD) relative to the X axis and the tangential tilt angle (TAN) relative to the Y axis.
FIG. 2 is a schematic perspective view illustrating the internal portion of a conventional optical disc drive. As shown in FIG. 2, a plurality of fixing structures 212, 214, 216, 218, 222, 224, 226 and 228 are disposed on a chassis 200 of the optical disc drive for installing the two guide rails 210 and 220. Moreover, resilience sheets 217, 227 and spring wires 215, 225 are employed for fixing the two guide rails 210 and 220.
As shown in FIG. 2, the primary guide rail 210 is penetrated through the two rail holes 102, 104 of the optical pickup head 100, and the secondary guide rail 220 is embedded into the rail notch 106. In such way, the optical pickup head 100 is movable on these two guide rails 210 and 220. Moreover, a spindle motor 230 is disposed on the chassis 200 of the optical disc drive. The optical disc (not shown) is placed on a turntable 232 of the spindle motor 230.
For adjusting the tilt of the optical pickup head 100, three screws 250, 260 and 270 are disposed on the chassis 200 of the optical disc drive for changing the altitudes of the guide rails 210 and 220 relative to the chassis 200. The screw 250 is used for changing the radial tilt angle (RAD) relative to the X axis. The screw 260 is used for changing the tangential tilt angle (TAN) relative to the Y axis. The screw 270 is used for changing the altitude of the optical pickup head 100.
From the above discussions, the conventional tilt adjusting device of the optical pickup head 100 uses three crews 250, 260 and 270 for adjusting the altitudes of the primary guide rail 210 and the both ends of the secondary guide rail 220. In such way, the angle between the optical pickup head 100 and the optical disc is adjusted.
The conventional tilt adjusting device, however, still has some drawbacks. For example, for adjusting the tilt of the optical pickup head, several resilience sheets, spring wires and screws are required to fix and adjust the guide rails. Since the conventional tilt adjusting device has too many parts and is assembled with high complexity, the cost of the parts and the assembling cost are increased.